Electric meter.



No. 773,837. PATENTED NOV. 1, 1904. E. R. WHITNEY.

ELECTRIC METER.

APPLICATION FILED FEB. 29, 1904.

N0 MODEL.

Fig.2.

UNTTED STATES Patented November 1, 1904.

PATENT OEETcE.

EDDY R. WHITNEY, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

ELECTRIC METER.

SPECIFICATION forming part of Letters Patent No. 773,837, dated November1, 1904:.

Application filed February 29, 1904. Serial No. 195,711. (No model.)

To all 1072 0111, it may concern:

Be it known that I, EDDY R. I/VHITNEY, a citizen of the United States,residing at Lynn, county of Essex, State of Massachusetts, have inventedcertain new and useful Improvements in Electric Meters, of which thefollowing is a specification.

The heating of electric motors and similar dynamo-electric machinesdepends upon the square of the current carried rather than upon thefirst power of the current. In driving machine-tools and for similarpurposes conditions are frequently encountered in which the load is ofan extremely variable nature. In some cases it is therefore'by the useof an ordinary ammeter a difiicult matter to determine the proper sizeof motor requisite for the work. This is due to the fact that at bestthe ammeter can give only an approximate idea of the mean current value,whereas the real quantity to be determined is the square root of themean square value of current, since upon the latter and not upon theformer depends the heating of the motor. I have therefore devised aninstrument which records or integrates thesquares of the various currentvalues flowing in a circuit throughout any given period. The readings ofthe instrument therefore furnish a measure of the heating of a machinein circuit therewith, and thus enables intelligent determination of thecapacity of machine necessary for the work.

In the drawings, Figure 1 represents one embodiment of my invention, andFig. 2 a modification.

In carrying my invention into practice I make use of a meter in whichthe torque is proportional to the square of the current. In order tomake the revolutions of the meter proportional to this quantity, Itherefore use a damping device proportional not to the square of thespeed, but to the first power thereof. Such an organization is shown inFig. 1. In this figure the armature of the meter is represented at 1 andthe field-winding at 2. The armature consists of a drumwinding, as usedin ordinary direct-current meters, and is provided with a commutator 3.The armature and field are connected in se- 5 ries with each other andare shunted about a resistance 4: in series with one of the mains 5 and6, in which the load-current flows. A damping-disk 7 and the usualpermanent magnets, such as 8 and 9, furnish the retarding torque. Acounter 10 records or registers the number of revolutions of the meter.

The shunt t diverts the greater part of the current from the meter, thusenabling the latter to be of small size, but at the same time causes thecurrent which does pass through the meter to be proportional to thetotal current. In order to render the effect'of the counterelectromotive force of the meter negligible, the field and armaturecircuit may be of considerable inherent resistance or may have anexternal resistance in series therewith.

If desired, in order to increase the torque of the instrument, and thusdiminish the percentage of error due to friction and similar causes, Imay pass the main current directly through the field-coils of the meter,as at 11 in Fig. 2, and supply only the armature, as at 12, with currentdiverted from the main circuit through the instrumentality of the seriesresistance or shunt 13. In other respects the arrangement shown in Fig.2 is the same as that in Fig. 1.

1n the foregoing description I have pointed out by Way of illustrationcertain embodiments of my invention. It will be evident,

however, that numerous variations therefrom may be made withoutdeparting from my invention.

What I claim as new, and desire to secure by Letters Patent of theUnited States. is

1. In an electric meter, the combination of a motor element the torqueof which is proproportional to the square of the current in portional tothe square of the current measthe circuit in Which the meter is used. 10ured, and a retarding device, the retarding In Witness whereof I haveset my hand this eifect of which is proportional to the first 25th dayof February, 190

5 power of the speed of the meter. EDDY R. "HITNEY.

2. An integratingmieter consisting of a Witnesses: 7 motor element and aretarding device so cor- DUGALD MOK. MoKILLoP,

related that the revolutions of the meter are ALEX. F. lVlAODONALD.

